Ink-jet devices in and of themselves are well known through e.g. U.S. Pat. Nos. 3,373,437 to Sweet et al; 3,560,988 to Krick; 3,579,721 to Kaltenbach; and 3,596,275 to Sweet. Typically, prior art ink-jet devices provide a linear array of fluid-jet orifices formed in an orifice plate from which filaments of pressurized marking fluid (e.g. ink, dye, etc.) are caused to issue from a fluid supply chamber. An individually controllable electrostatic charging electrode is disposed downstream of the orifice plate along the so-called "drop-formation" zone. In accordance with known principles of electrostatic induction, the fluid filament is caused to assume an electrical potential opposite in polarity and related in magnitude to the electrical potential of its respective charging electrode. When a droplet of fluid is separated from the filament, this induced electrostatic charge is then trapped on and in the droplet. Thus, subsequent passage of the charged droplet through an electrostatic field will cause the droplet to be deflected towards a catching structure. Uncharged droplets on the other hand proceed along the normal droplet flight path and are eventually deposited upon a recording substrate.
It has previously been known to use solder techniques to rigidly fix an orifice plate to an orifice plate holder. However, such previous solder techniques are disadvantageous in that bowing of the orifice plate occurs due to differential thermal expansion and temperature variances between the orifice plate and the orifice plate holder. This phenomenon is, at least in part, thought to be caused by the fact that the solder technique precludes intimate planar contact between the various structural components.
Recently it has been proposed to utilize ink-jet devices as a means to print patterns or the like on textile materials, attention being directed to commonly owned U.S. Ser. No. 428,490 to Gamblin filed Sept. 28, 1982, which is expressly incorporated herein by reference. In order to achieve fine printing of patterns on a textile substrate, it is necessary to utilize an orifice plate having a linear array of very small orifices sized in the range of, for example, 0.00035 to 0.020 inch diameters. A problem exists with the use of such small-sized orifices in that mechanical bending or "bowing" in the longitudinal axis of the orifice plate detrimentally affects the print quality. That is, mechanical bending of the orifice plate results in the imprecise formation or sequencing of fluid droplet streams issuing from the orifices thereby deleteriously affecting the subsequent controlled charging and/or deflection thereof from a predetermined flight path.
By way of the present invention, such disadvantages have been overcome by providing a novel mounting assembly which minimally stresses the orifice plate laterally of the linear array of orifices so as to prevent its axial bowing. In one method according to the present invention, the orifice plate is thermally expanded and then allowed to cool while maintaining the expanded length so as to tension the orifice plate between its opposing ends. In an alternative method according to the invention, a stretching (tensioning) apparatus places the orifice plate under tension prior to its being clamped into position on the fluid jet manifold assembly. In this second method, the mechanical tensioning is done in lieu of tensioning by thermally expanding and cooling the orifice plate. Both methods contribute to maintaining the planar nature of the orifice plate and thus significantly reduce any potential orifice plate deformation.